Diagnostic Aids
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- The Crankshaft Position System Variation Learn procedure may need to be performed. Refer to Crankshaft Position System Variation Learn
- Ensure that each fuel injector is connected to the proper fuel injector harness connector. Refer to Engine Controls Schematics (Except LZ1)
- A high resistance condition on any fuel injector control circuit can cause an engine misfire P0300-P0308 DTC to set without setting a fuel injector circuit P0201-P0208 DTC.
- A high resistance condition on any ignition control (IC) circuit can cause an engine misfire P0300-P0308 DTC to set without setting an IC circuit P0351-P0358 DTC.
- A misfire may only occur when the engine is operating under a load or when the engine is cold.
- A misfire DTC could be caused by an excessive vibration from sources other than the engine. Inspect the following for possible sources of vibration:
- A tire or wheel that is out of round or balance
- Variable thickness brake rotors
- An unbalanced drive shaft
- Broken or weak valve springs
- Cracked spark plug insulators
- Certain rough road conditions
- A damaged accessory drive component or belt; remove the belt and safely operate the engine to evaluate if the misfire counts go away.
- A damaged reluctor wheel